A 26 year old man complains of abdominal distension, swelling of the legs and easy fatigability. His blood pressure is 90/70 mm Hg and pulse becomes difficult to feel on inspiration. JVP is grossly elevated and rises further on deep inspiration. He has pedal edema, ascites and tender hepatomegaly. Precordium is quiter with loud and some what early apical third heart sound. The probable diagnosis is -